Note: Descriptions are shown in the official language in which they were submitted.
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POLYCRYSTALLINE DIAMOND COMPOSITE CONSTRUCTIONS COMPRISING
THERMALLY STABLE DIAMOND VOLUME
FIELD OF THE INVENTION
This invention generally relates to diamond bonded composite materials and,
more specifically, diamond bonded composite materials and compacts formed
therefrom that are
specially designed to provide improved thermal stability when compared to
conventional
polycrystalline diamond.
BACKGROUND OF THE INVENTION
Polycrystalline diamond (PCD) materials and PCD elements formed therefrom
are well known in the art. Conventional PCD is formed by combining diamond
grains with a
suitable solvent catalyst material to form a mixture. The mixture is subjected
to processing
conditions of extremely high pressure/high temperature, where the solvent
catalyst material
promotes desired intercrystalline diamond-to-diamond bonding between the
grains, thereby
forming a PCD structure. The resulting PCD structure produces enhanced
properties of wear
resistance and hardness, making PCD materials extremely useful in aggressive
wear and cutting
applications where high levels of wear resistance and hardness are desired.
Solvent catalyst materials typically used for forming conventional PCD include
solvent metals from Group VIII of the Periodic table, with cobalt (Co) being
the most common.
Conventional PCD can comprise from 85 to 95% by volume diamond and a remaining
amount of
the solvent metal catalyst material. The solvent catalyst material is present
in the microstructure
of the PCD material within interstices that exist between the bonded together
diamond grains.
A problem known to exist with such conventional PCD materials is thermal
degradation due to differential thermal expansion characteristics between the
interstitial solvent
catalyst material and the intercrystalline bonded diamond. Such differential
thermal expansion is
known to occur at temperatures of about 400°C, causing ruptures to
occur in the diamond-to-
diamond bonding, and resulting in the formation of cracks and chips in the PCD
structure.
Another problem known to exist with conventional PCD materials is also related
to the presence of the solvent catalyst material in the interstitial regions
and the adherence of the
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solvent catalyst to the diamond crystals, and is known to cause another form
of thermal
degradation. Specifically, the solvent catalyst material causes an undesired
catalyzed phase
transformation to occur in diamond (converting it to carbon monoxide, carbon
dioxide, or
graphite) with increasing temperature, thereby limiting practical use of such
conventional PCD
material to about 750°C.
Attempts at addressing such unwanted forms of thermal degradation in PCD are
known in the art. Generally, these attempts have involved modifying the PCD
body in such a
manner as to provide an improved degree of thermal stability at the wear or
cutting surface of the
body when compared to the conventional PCD material discussed above. One known
attempt at
producing a thermally stable PCD body involves at least a two-stage process of
first forming a
conventional sintered PCD body, by combining diamond grains and a cobalt
solvent catalyst
material and subjecting the same to high pressure/high temperature process,
and then removing
the solvent catalyst material therefrom.
This method, which is fairly time consuming, produces a resulting PCD body
that
is substantially free of the solvent catalyst material, and is therefore
promoted as providing a
PCD body having improved thermal stability. However, the resulting thermally
stable PCD
body typically does not include a metallic substrate attached thereto by
solvent catalyst
infiltration from such substrate due to the solvent catalyst removal process.
The thermally stable
PCD body also has a coefficient of thermal expansion that is sufficiently
different from that of
conventional substrate materials (such as WC-Co and the like) that are
typically infiltrated or
otherwise attached to the PCD body to provide a PCD compact that adapts the
PCD body for use
in many desirable applications. This difference in thermal expansion between
the thermally
stable PCD body and the substrate, and the poor wetability of the thermally
stable PCD body
diamond surface makes it very difficult to bond the thermally stable PCD body
to conventionally
used substrates, thereby requiring that the PCD body itself be attached or
mounted directly to a
device for use.
However, since such conventional thermally stable PCD body is devoid of a
metallic substrate, it cannot (e.g., when configured for use as a drill bit
cutter) be attached to a
drill bit by conventional brazing process. The use of such thermally stable
PCD body in this
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particular application necessitates that the PCD body itself be mounted to the
drill bit by
mechanical or interference fit during manufacturing of the drill bit, which is
labor intensive, time
consuming, and which does not provide a most secure method of attachment.
Additionally, because such conventional thermally stable PCD body no longer
includes the solvent catalyst material, it is known to be relatively brittle
and have poor impact
strength, thereby limiting its use to less extreme or severe applications and
making such
thermally stable PCD bodies generally unsuited for use in aggressive
applications such as
subterranean drilling and the like.
Another approach has been to form a diamond body onto the metallic substrate
by
the process of chemical or plasma vapor deposition (CVD or PVD). Deposition of
diamond by
CVD or PVD process is one that results in the formation of an intercrystalline
diamond bonded
structure on the substrate that is substantially free of any solvent metal
catalyst. A first problem,
however, with this approach is the relatively long amount of time associated
with developing a
diamond body on the substrate that has a having meaningful diamond body
thickness. Another
problem with this approach is that the diamond body that is formed from CVD or
PVD technique
is one that is known to be relatively brittle, when compared to conventional
PCD, and thus is
susceptible to cracking when placed into a cutting or wear application. A
still further problem
with this approach is that the diamond body formed by CVD or PVD technique is
one that has a
relatively weak interface with the metallic substrate, and thus one that is
susceptible to separating
from the substrate when placed into a cutting or wear application.
It is, therefore, desired that a diamond material be developed that has
improved
thermal stability when compared to conventional PCD materials. It is also
desired that a
diamond compact be developed that includes a thermally stable diamond material
bonded to a
suitable substrate to facilitate attachment of the compact to an application
device by conventional
method such as welding or brazing and the like. It is further desired that
such thermally stable
diamond material and compact formed therefrom display properties of
hardness/toughness and
impact strength that are comparable to conventional thermally stable PCD
material described
above, and PCD compacts formed therefrom. It is further desired that such a
product can be
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manufactured at reasonable cost without requiring excessive manufacturing
times and without
the use of exotic materials or techniques.
SUMMARY OF THE INVENTION
PCD composite constructions of this invention are generally provided in the
form
of a compact comprising a diamond bonded body that is bonded to a substrate.
The diamond
bonded body comprises a thermally stable region that extends a distance below
a diamond
bonded body surface. The thermally stable region has a material microstructure
consisting
essentially of a single phase of diamond crystals that are bonded together. In
a preferred
embodiment, the thermally stable region has a diamond volume content of
approximately 100
percent. The diamond bonded body includes a PCD region that extends from the
thermally
stable region and is bonded to the thermally stable region. The PCD region
comprises bonded
together diamond crystals, interstitial regions interposed between the diamond
crystals, and a
solvent catalyst material. In a preferred embodiment, the PCD region has a
diamond volume
content of approximately 95 percent, and in some instances in the range of
from about 75 percent
to about 99 percent.
The PCD composite constructions in the form of compacts are prepared by
combining a first volume of diamond crystal-containing material, comprising
bonded together
diamond crystals and interstitial regions interposed between the diamond
crystals, wherein a
metal solvent catalyst material is disposed within the interstitial regions,
with a second volume of
diamond crystal-containing material consisting essentially of a single phase
of bonded together
diamond crystals. The first volume of diamond crystal-containing material is
in contact with a
substrate, and wherein the first volume of diamond-containing material, the
second volume of
diamond-containing material, and the substrate comprise an assembly. The
assembly is then
subjected to high pressure/high temperature conditions to form a diamond
bonded body attached
to the substrate. The diamond body comprises a PCD region formed from the
first diamond
crystal-containing material, and a thermally stable diamond bonded region that
is formed from
the second diamond-containing material. The PCD region and the thermally
stable diamond
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bonded region are integrally joined together, and the thermally stable diamond
bonded region is
positioned along a working surface of the compact.
PCD composite constructions and compacts of this invention can be used as
cutting elements on drill bits used for drilling subterranean formations. PCD
composite
constructions of this invention formed according to the principles of this
invention have
improved thermal stability when compared to conventional PCD materials, and
include a
substrate for purposes of facilitating attachment of the diamond bonded
compact to an
application device by conventional methods such as welding or brazing and the
like. Further,
PCD composite constructions and compacts of this invention display properties
of
hardness/toughness and impact strength that are comparable to conventional
thermally stable
PCD materials described above, and PCD compacts formed therefrom.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features and advantages of the present invention will be
appreciated as the same becomes better understood by reference to the
following detailed
description when considered in connection with the accompanying drawings
wherein:
FIG. lA is a schematic view of a thermally stable diamond bonded region of a
polycrystalline diamond composite of this invention;
FIG. 1 B is a back-scatter electron micrograph illustrating a region of the
polycrystalline diamond composite of this invention comprising the thermally
stable diamond
bonded region joined to a polycrystalline diamond region;
FIG. 2 is a perspective view of a polycrystalline diamond composite compact of
this invention;
FIG. 3 is a cross-sectional schematic view of an embodiment of the
polycrystalline diamond composite compact of this invention;
FIG. 4 is a perspective side view of an insert, for use in a roller cone or a
hammer
drill bit, comprising the polycrystalline composite compact of this invention;
FIG. 5 is a perspective side view of a roller cone drill bit comprising a
number of
the inserts of FIG. 4;
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FIG. 6 is a perspective side view of a percussion or hammer bit comprising a
number of inserts of FIG. 4;
FIG. 7 is a schematic perspective side view of a diamond shear cutter
comprising
the thermally stable diamond bonded compact of FIGS. 2 and 3; and
FIG. 8 is a perspective side view of a drag bit comprising a number of the
shear
Gutters of FIG. 7.
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DETAILED DESCRIPTION
PCD composite materials comprising thermally stable diamond volumes and
compacts of this invention are specifically engineered having a diamond body
that is a composite
construction comprising a PCD region and a thermally stable diamond bonded
region, thereby
providing a diamond body having an improved degree of thermal stability when
compared to
conventional PCD materials. Additionally, PCD composite materials of this
invention can be
provided in the form of a compact that comprises the above-noted diamond body
joined to a
substrate.
As used herein, the term "PCD" is used to refer to polycrystalline diamond
that
has been formed at high pressure/high temperature (HPHT) conditions through
the use of a metal
solvent catalyst. Suitable metal solvent catalysts include, but are not
limited to, those metals
included in Group VIII of the Periodic table. The thermally stable diamond
bonded region or
volume in diamond bonded bodies of this invention, is not referred to as PCD
because, unlike
conventional PCD and thermally stable PCD that is formed by removing the
solvent metal
catalyst from PCD, it is fabricated by a different process.
As noted above, PCD composite materials of this invention include a region or
volume that comprises conventional PCD, i.e., intercrystalline bonded diamond
formed using a
metal solvent catalyst, thereby providing properties of hardness/toughness and
impact strength
that are superior to conventional thermally stable PCD materials that have
been rendered
thermally stable by having substantially all of the solvent catalyst material
removed. Such PCD
region also enables the diamond body of PCD composite materials of this
invention to be
permanently attached to a substrate by virtue of the presence of such metal
solvent catalyst. This
feature enables PCD composite materials of this invention to be used in the
form of wear and/or
cutting elements that can be attached to wear and/or cutting, such as
subterranean drill bits, by
conventional attachment means such as by brazing and the like.
PCD composite materials of this invention are formed using one or more HPHT
processes. In an example embodiment, a first HPHT process is used to form the
PCD region of
the diamond body and attach the body to a desired substrate, and a second HPHT
process may be
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used to consolidate a thermally stable diamond region, volume or body and
attach the same to
the PCD region, thereby forming the PCD composite material.
FIG. 1 A schematically illustrates a section taken from a thermally stable
diamond
bonded region 10 of the diamond body of this invention. The thermally stable
diamond bonded
region 10 is one having a material microstructure comprising a plurality of
diamond crystals 12
that are bonded to one another. Unlike conventional thermally-stable PCD, that
is formed from
conventional PCD that is subsequently treated to remove the solvent metal
catalyst material
thereby leaving open interstitial spaces between the bonded diamond crystals,
the thermally
stable diamond bonded region 10 of the diamond body of this invention is
formed without using
a catalyst metal solvent. Thereby producing a diamond bonded region that is
inherently
thermally stable and that does not include the open interstitial spaces, voids
or regions between
the diamond bonded crystals, i.e., it is essentially pure carbon with no
binder phase.
It is to be understood that the diamond crystals 12 shown in FIG. lA are
configured having generally irregular shapes for purposes of illustration and
reference. It is to be
understood that the diamond crystals in the thermally stable diamond bonded
can be configured
having a variety of different shapes depending on such factors as the process
and type of
diamond that is used to form such region. For example, as described below and
illustrated in
FIG. 1 B, the diamond crystals in this region can be configured having a
columnar structure when
the diamond is provided as material made by chemical vapor deposition (CVD
diamond).
Methods useful for forming the thermally stable diamond bonded material can be
any process that is known to create a volume of bonded diamond crystals that
is essentially free
of interstitial regions or any other second phase material. Methods known to
provide such a
desired volume of diamond bonded crystals, with a diamond volume density or
content of
essentially 100 percent, include chemical vapor deposition (CVD) and plasma
vapor deposition
(PVD). The CVD or PVD methods useful for producing the thermally stable
diamond bonded
region of the diamond body of this invention include those known in the art
for otherwise
producing layers or regions of exclusively bonded diamond crystals. Such
methods generally
involve a crystal growth process, whereby solid diamond bonded material is
formed from a gas
or plasma phase using a reactive gas mixture that supplies the necessary
active species, i.e.,
CA 02556052 2006-08-02
carbon, onto a controlled surface. A desired characteristic of such diamond
material provided by
using CVD and/or PVD process is that it have a very high purity level and does
not include any
binder agent or other second phase that could otherwise adversely impact
thermal stability of the
bonded diamond crystals.
FIG. 1 B is a back-scatter electron micrograph illustrating a selected region
of an
example embodiment diamond bonded composite 13 of this invention comprising a
diamond
bonded region 14 that is joined to a polycrystalline diamond region 15. In
this particular
example, the diamond bonded region is formed by CVD that produces columnar
diamond
structure as illustrated. The polycrystalline diamond region 15 is shown to
comprise a plurality
of diamond crystals 16 (shown as the dark phases) with a metal solvent
catalyst material 17
(shown as the white phases) disposed within interstitial regions between the
diamond crystals.
In an example embodiment, the thermally stable diamond bonded material is
formed using a CVD or PVD process to provide a material microstructure
comprising a plurality
of diamond bonded crystals having an average particle size in the range of
from about
0.01 to 2,000 micrometers, and preferably in the range of from about 1 to
1,000 micrometers,
and more preferably in the range of from about 5 to 300 micrometers. A
thermally stable
diamond bonded material comprising bonded together diamond crystals within the
above particle
size range provides desired properties of wear resistance and hardness that
are especially well
suited for such aggressive wear and/or cutting applications as for use with
subterranean drill bits.
However, it is to be understood that the particular particle size of the
diamond crystals used to
form the thermally stable diamond bonded material can and will vary depending
on such factors
as the thickness of the thermally stable diamond bonded material region, and
the end use
application.
FIG. 2 illustrates a PCD composite material compact 18 constructed according
to
principles of this invention. Generally speaking, the compact 18 comprises a
diamond bonded
body 19 having the thermally stable diamond bonded region 20 as described
above, a
conventional PCD region 21, and a substrate 22, e.g., a metallic substrate,
attached to the PCD
region 20. While the PCD composite material compact 18 is illustrated as
having a certain
configuration, it is to be understood that PCD composite material compacts of
this invention can
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be configured having a variety of different shapes and sizes depending on the
particular wear
and/or cutting application.
In an example embodiment, the compact 18 is formed by using two HPHT
processes. In a first HPHT process, the conventional PCD region 21 is formed,
i.e., it is
consolidated and sintered, and is joined to the desired substrate 22. Diamond
grains useful for
forming the PCD region 21 include synthetic diamond powders having an average
diameter grain
size in the range of from submicrometer in size to 100 micrometers, and more
preferably in the
range of from about 5 to 80 micrometers. The diamond powder can contain grains
having a
mono or multi-modal size distribution. In an example embodiment, the diamond
powder has an
average particle grain size of approximately 20 micrometers. In the event that
diamond powders
are used having differently sized grains, the diamond grains are mixed
together by conventional
process, such as by ball or attrittor milling for as much time as necessary to
ensure good uniform
distribution. The diamond powder may be combined with a desired solvent metal
catalyst
powder to facilitate diamond bonding during the HPHT process and/or the
solvent metal catalyst
can be provided by infiltration from the substrate. The diamond grain powder
is preferably
cleaned, to enhance the sinterability of the powder by treatment at high
temperature, in a vacuum
or reducing atmosphere.
Alternatively, the diamond powder mixture can be provided in the form of a
green-state part or mixture comprising diamond powder that is contained by a
binding agent,
e.g., in the form of diamond tape or other formable/confirmable diamond
mixture product to
facilitate the manufacturing process. In the event that the diamond powder is
provided in the
form of such a green-state part it is desirable that a preheating step take
place before HPHT
consolidation and sintering to drive off the binder material. In an example
embodiment, the PCD
material resulting from the above-described HPHT process has a diamond volume
content of
approximately 95 percent, but other embodiments may fall in the range of from
about 75 to about
99 volume percent.
The diamond powder mixture is loaded into a desired container for placement
within a suitable HPHT consolidation and sintering device. In an example
embodiment, where
PCD composite material is provided in the form of a compact and the PCD region
21 is to be
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attached to a substrate, a suitable substrate material is disposed within the
consolidation and
sintering device adjacent the diamond powder mixture.
In a preferred embodiment, the substrate 22 is provided in a preformed state.
Substrates useful for forming PCD composite compacts of this invention can be
selected from
the same general types of materials conventionally used to form substrates for
conventional PCD
materials, including carbides, nitrides, carbonitrides, ceramic materials,
metallic materials,
cermet materials, and mixtures thereof. A feature of the substrate is that it
include a metal
solvent catalyst that is capable of melting and infiltrating into the adjacent
volume of diamond
powder to both facilitate conventional diamond-to-diamond intercrystalline
bonding forming the
PCD region, and to form a secure attachment between the PCD region and
substrate. Suitable
metal solvent catalyst materials include those metals selected from Group VIII
elements of the
Periodic table. A particularly preferred metal solvent catalyst is cobalt
(Co), and a preferred
substrate material is cemented tungsten carbide (WC-Co).
According to this method of making the compact, the container containing the
diamond power and the substrate is loaded into the HPHT device and the device
is then activated
to subject the container to a desired HPHT condition to effect consolidation
and sintering of the
diamond powder. In an example embodiment, the device is controlled so that the
container is
subjected to a HPHT process having a pressure of approximately 5,500 Mpa and a
temperature
of from about 1,350°C to 1,500°C for a predetermined period of
time. At this pressure and
temperature, the solvent metal catalyst melts and infiltrates into the diamond
powder mixture,
thereby sintering the diamond grains to form conventional PCD, and forming a
desired
attachment or bond between the PCD region of the diamond bonded body and the
substrate.
While a particular pressure and temperature range for this HPHT process has
been
provided, it is to be understood that such processing conditions can and will
vary depending on
such factors as the type and/or amount of metal solvent catalyst used in the
substrate, as well as
the type and/or amount of diamond powder used to form the PCD region. After
the HPHT
process is completed, the container is removed from the HPHT device, and the
assembly
comprising the bonded together PCD region and substrate is removed from the
container.
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The thermally stable diamond bonded material is then provided onto a
designated
surface of the PCD region of the assembly that will ultimately form the
thermally stable surface
of the diamond body and the PCD composite material compact. In an example
embodiment, the
thermally stable diamond bonded material is provided onto one or more surface
of the PCD
region that will ultimately define a wear and/or cutting surface of the
diamond body and
compact, to thereby provide improved properties of thermal stability at such
surface.
The thermally stable diamond bonded material can be provided onto the surface
of the PCD region by different methods. According to a first method, a desired
thickness of
thermally stable bonded diamond is grown separately from the PCD region as its
own
independent body or layer that is subsequently joined to the PCD region by a
second HPHT
process described below. This method of making the thermally stable diamond
bonded material
is useful for end use applications calling for a relatively thick thermally
stable diamond bonded
region, e.g., for applications calling for high levels of thermal stability,
hardness and/or wear
resistance. The thermally stable diamond bonded material body that is formed
according to this
method may have an average thickness of from about 10 microns to 3,000
microns, and
preferably in the range of from about 100 microns to 1,000 microns. It is to
be understood that
this thickness is the thickness of the thermally stable diamond bonded
material or body before it
is joined to the PCD region by the second HPHT process.
Alternatively, the thermally stable diamond bonded material can be provided
according to a second method that involves growing the bonded diamond onto the
surface of the
PCD region itself by the CVD or PVD process noted above. Prior to growing the
layer, it may
be necessary to treat the target surface of the PCD region in a manner that
promotes growth of
the thermally stable diamond bonded material thereon. This second method may
be useful for
end use applications calling for a relatively thin thermally stable diamond
bonded region, e.g.,
for applications not calling for high levels of thermal stability, hardness
and/or wear resistance.
Accordingly, this second method of supplying the thermally stable diamond
bonded material
may be useful for providing such regions having an average thickness of from
about 0.01
microns to 100 microns, and preferably in the range of from about 0.1 microns
to 20 microns.
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After the thermally stable diamond bonded material is formed, the assembly
comprising the already joined together substrate and PCD region and the
thermally stable
diamond bonded material (whether provided in the form of an independent body
or grown on the
PCD region) is placed into an appropriate container and loaded into the HPHT
device. The
HPHT device is operated to impose a desired pressure and elevated temperature
on the assembly
to cause the thermally stable diamond bonded material to be joined to the PCD
region, thereby
completing formation of the diamond body and the PCD composite compact.
In an example embodiment, the second HPHT process is operated at a pressure
and temperature condition that is sufficient to cause the solvent metal
catalyst in the PCD region
adjacent the thermally stable diamond bonded material to melt and to cause the
diamond crystals
along the interface between the PCD region and the thermally stable diamond
bonded material to
bond together. Additionally, during this HPHT process the thermally stable
diamond bonded
material is consolidated to form the thermally stable diamond bonded region of
the diamond
body. The HPHT process conditions can be the same as that disclosed above for
the first HPHT
process or can be different, e.g., can be operated at a higher temperature
and/or pressure to
impose a desired change on the physical properties of the diamond in one or
both of the regions.
While this is one way of making the PCD composite compacts of this invention,
there are other methods that are understood to be within the scope and
practice of this invention.
For example, rather than starting with a mixture of diamond powder and a
substrate and
subjecting the same to a first HPHT process to form a sintered substrate and
PCD region
assembly for subsequent combination with the thermally stable diamond bonded
material, one
can start with a sintered PCD body. In such case, the thermally stable diamond
bonded material
can be combined with the sintered PCD body according to either of the methods
described
above, and the combination of the substrate, the sintered PCD body and the
thermally stable
diamond bonded material can be placed in an appropriate container and loaded
into the HPHT
device.
The device can be operated at the same conditions noted above for the first or
second HPHT process for the purpose of consolidating the thermally stable
diamond bonded
material, sintering it to the PCD region, and joining the PCD region to the
substrate. This
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method could be useful in situations where the PCD material is available in
sintered form, and
would thus enable formation of the PCD composite compact of this invention by
a single HPHT
process.
Alternatively, rather than being provided after formation of the PCD region,
the
thermally stable diamond bonded material can be provided during an earlier
stage of production
that would enable formation of the PCD composite compact via a single HPHT
process. In such
alternative method of making, thermally stable diamond bonded material can be
formed as an
independent body in the manner described above, and can be combined with the
diamond
powder used to form the PCD region. Specifically, the thermally stable diamond
bonded
material body would be positioned within the container adjacent a designated
surface of the
diamond powder to form the thermally stable diamond bonded region in the
sintered diamond
body.
The substrate would also be positioned adjacent another surface of the diamond
powder, and the container would be loaded into the HPHT device and subjected
to the same
pressure and temperature conditions noted above for the first HPHT process to
form the PCD
region, consolidate the thermally stable diamond bonded material, sinter the
PCD region to the
thermally stable diamond bonded material, and bond the PCD region to the
substrate, thereby
forming the PCD composite compact during a single HPHT process.
FIG. 3 illustrates another embodiment PCD composite compact 24 constructed
according to principles of the invention. The PCD composite compact of this
embodiment
comprises a diamond body 26 attached to a substrate 28, wherein the diamond
body has a
working surface 30 positioned along an outermost top portion of the body that
is formed from the
thermally stable diamond bonded region 32. The diamond body includes the PCD
region 34 that
is interposed between the thermally stable diamond bonded region and the
substrate. In this
particular embodiment, the PCD region 34 comprises two different PCD material
layers 36 and
38.
The PCD layers 36 and 38 each comprise PCD materials that have one or more
property that is different from one another. For example, the PCD materials in
these layers may
be formed from differently sized diamond grains and/or have a different
diamond volume
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content or density. For example, the diamond volume content in the PCD
material layer 38
adjacent the substrate may be less than that of the diamond volume content in
the PCD material
layer 36.
The different PCD material layers can be formed in the manner described above
by assembling different volumes of the different diamond powders into the
container for HPHT
processing, or by using different green-state parts having the above noted
different properties.
While FIG. 3 illustrates an embodiment of the PCD composite compact comprising
a PCD
region 34 made from two different PCD material layers 36 and 38, it is to be
understood that this
example embodiment is provided for purposes of reference and that PCD
composite compacts of
this invention can comprise a diamond body comprising a PCD region comprising
any number of
PCD material layers.
Alternatively, instead of comprising complete layers, the thermally stable
diamond bonded region and/or the PCD region can be configured such that one or
both occupy a
portion of the volume of the diamond body. For example, the PCD region can be
configured to
occupy the bulk of the diamond body or table and the thermally stable diamond
bonded region
can be configured to occupy a small or partial volume positioned at or
adjacent a working
surface of the diamond body, which working surface can be positioned anywhere
along an
outside surface of the diamond body, e.g., along a top or side surface.
Alternatively, instead of comprising multiple discrete layers, the PCD region
can
be configured such that desired different properties in the PCD region is
provided in the form of
a continuum rather than as a step change. For example, the PCD region can be
configured
having a diamond volume content that changes as a function of distance moving
away from the
substrate. Accordingly, it is to be understood that such variations in the PCD
region of such
example embodiment PCD composite compacts are to be within the scope of this
invention.
PCD composite compacts formed in accordance with the principles of this
invention may have a PCD region thickness and substrate thickness that can and
will vary
depending on the particular end use application. In an example embodiment, for
example when
the PCD composite compact of this invention is provided in the form of a
cutting element such
as a shear cutter for use with a subterranean drill bit, the PCD composite
compact may comprise
CA 02556052 2006-08-02
a PCD region having a thickness of at least about 50 micrometers. In an
example embodiment,
the thickness of the PCD region can be in the range of from about
100 micrometers to 5,000 micrometers, preferably in the range of from about
1,000 micrometers
to 3,000 micrometers.
The PCD composite compact may have a substrate thickness in the range of from
about 2,000 micrometers to 20,000 micrometers, preferably in the range of from
about
3,000 micrometers to 16,000 micrometers, and more preferably in the range of
from about
5,000 micrometers to 13,000 micrometers. Again, it is to be understood that
the exact thickness
of the PCD region and substrate will vary on the end use application as well
as the overall size of
the PCD composite compact.
The above-described PCD composite materials and compacts formed therefrom
will be better understood with reference to the following example:
Example - PCD Composite Compact
Synthetic diamond powders having an average grain size of approximately 2-50
micrometers were mixed together for a period of approximately 2 to 6 hours by
ball milling. The
resulting mixture was cleaned by heating to a temperature in excess of about
850°C under
vacuum. The mixture was loaded into a refractory metal container and a
preformed WC-Co
substrate was positioned adjacent the diamond powder volume. The container was
surrounded
by pressed salt (NaCI) and this arrangement was placed within a graphite
heating element. This
graphite heating element containing the pressed salt and the diamond powder
and substrate
encapsulated in the refractory container was then loaded in a vessel made of a
high-
temperature/high-pressure self sealing powdered ceramic material formed by
cold pressing into a
suitable shape.
The self sealing powdered ceramic vessel was placed in a hydraulic press
having
one or more rams that press anvils into a central cavity. A first HPHT process
was provided by
operating the press to impose a processing pressure and temperature condition
of approximately
S,SOOMPa and approximately 1,300 to 1,500°C on the vessel for a period
of approximately 20
minutes. During this first HPHT process, cobalt from the WC-Co substrate
infiltrated into an
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adjacent region of the diamond powder mixture and facilitated intercrystalline
diamond bonding
to form conventional PCD, thereby forming the PCD region of the PCD composite
diamond
body, and also joining the PCD region to the substrate. The vessel was opened
and the resulting
assembly of the PCD region and the substrate was removed. The so-formed PCD
region had a
diamond volume content density of approximately 85 percent.
A thermally stable diamond bonded material was provided in the form of a
preformed CVD body having a thickness of approximately 300 microns, and having
an average
particle size of about 100 microns. It is to be understood that the average
particle size of
diamond formed by CVD can and will vary through the layer thickness, generally
increasing
along the growth direction. Such crystals are typically in the form of
elongated needles having
large aspect ratios. The CVD body was positioned adjacent a surface of the PCD
region and the
combination of the CVD body and the assembly of the PCD region and substrate
was loaded into
a refractory metal container that was again surrounded by pressed salt and
placed within a
graphite heating element. The graphite heating element containing the pressed
salt and the
container was then loaded in a vessel made of a high-temperature/high-pressure
self sealing
powdered ceramic material formed by cold pressing into a suitable shape.
The self sealing powdered ceramic vessel was placed in a hydraulic press
having
one or more rams that press anvils into a central cavity. A second HPHT
process was provided
by operating the press was operated to impose a processing pressure and
temperature condition
of approximately 5,500 MPa and approximately 1,500 °C on the vessel for
a period of
approximately 20 minutes. During this second HPHT processing step, cobalt from
the PCD
region melts and infiltrates to the surface of the CVD body and facilitates
sintering and diamond
bonding between the diamond crystals at the interface of the PCD region and
the CVD body to
form integrally join the two diamond bonded regions together, thereby forming
the resulting
diamond bonded body. Additionally, during this second HPHT process, the CVD
body is
consolidated to form the thermally stable diamond bonded region.
The vessel was opened and the resulting assembly PCD composition compact of
this invention comprising the substrate integrally joined to the diamond body,
comprising the
PCD region and the thermally stable diamond bonded region, was removed
therefrom.
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Examination of the PCD compact revealed that the thermally stable diamond
bonded region was
well bonded to the PCD region. The so-formed PCD compact had a substrate
thickness of
approximately 11,000 microns, a PCD region thickness of approximately 2,000
microns, and a
thermally stable diamond bonded region thickness of approximately 300 microns,
and was
provided in the form of a cutting element to be used with a fixed cone
subterranean drill bit.
A feature of PCD composite materials and compacts of this invention is that
they
comprise a diamond bonded body having both a thermally stable diamond bonded
region,
positioned along a working wear and/or cutting surface, and a conventional PCD
region. In a
preferred embodiment, the thermally stable diamond bonded region is
characterized by having
essentially no interstitial regions, voids or spaces, and that comprises a
diamond volume density
of essentially 100 percent. The presence of these different diamond bonded
regions provides a
composite diamond bonded body having improved properties of thermal stability,
wear
resistance and hardness where it is needed most, i.e., at the working surface,
while also
comprising a PCD region interposed between the thermally stable diamond bonded
region and
the substrate to both facilitate attachment of the thermally stable diamond
bonded region thereto,
when the thermally stable diamond bonded region is provided as CVD or PVD
diamond, and to
facilitate attachment of the diamond body to the substrate.
Another feature of PCD composite compacts of this invention is the fact that
they
include a substrate, thereby enabling compacts of this invention to be
attached by conventional
methods such as brazing or welding to variety of different cutting and wear
devices to greatly
expand the types of potential use applications for compacts of this invention.
PCD composite materials and compacts of this invention can be used in a number
of different applications, such as tools for mining, cutting, machining and
construction
applications, where the combined properties of thermal stability, wear and
abrasion resistance are
highly desired. PCD composite materials and compacts of this invention are
particularly well
suited for forming working, wear and/or cutting components or elements in
machine tools and
drill and mining bits, such as fixed and roller cone rock bits used for
subterranean drilling
applications.
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FIG. 4 illustrates an embodiment of a PCD composite compact of this invention
provided in the form of an insert 40 used in a wear or cutting application in
a roller cone drill bit
or percussion or hammer drill bit used for subterranean drilling. For example,
such inserts 40
can be formed from blanks comprising a substrate portion 41 formed from one or
more of the
substrate materials disclosed above, and a diamond bonded body 42 having a
working surface
formed from the thermally stable diamond bonded region of the diamond bonded
body. The
blanks are pressed or machined to the desired shape of a roller cone rock bit
insert.
FIG. 5 illustrates a rotary or roller cone drill bit in the form of a rock bit
43
comprising a number of the wear or cutting inserts 40 disclosed above and
illustrated in FIG. 4.
The rock bit 43 comprises a body 44 having three legs 46, and a roller cutter
cone 48 mounted on
a lower end of each leg. The inserts 40 can be fabricated according to the
method described
above. The inserts 40 are provided in the surfaces of each cutter cone 48 for
bearing on a rock
formation being drilled.
FIG. 6 illustrates the inserts 40 described above as used with a percussion or
hammer bit 50. The hammer bit comprises a hollow steel body 52 having a
threaded pin 54 on
an end of the body for assembling the bit onto a drill string (not shown) for
drilling oil wells and
the like. A plurality of the inserts 40 are provided in the surface of a head
56 of the body 52 for
bearing on the subterranean formation being drilled.
FIG. 7 illustrates a PCD composite compact of this invention embodied in the
form of a shear cutter 58 used, for example, with a drag bit for drilling
subterranean formations.
The shear cutter 58 comprises a diamond bonded body 60, comprising both a PCD
region and a
thermally stable diamond bonded region, sintered or otherwise attached to a
cutter substrate 62.
The diamond bonded body includes a working or cutting surface 64 that is
formed from the
thermally stable region of the diamond bonded body.
FIG. 8 illustrates a drag bit 66 comprising a plurality of the shear Gutters
58
described above and illustrated in FIG. 7. The shear Gutters are each attached
to blades 70 that
each extend from a head 72 of the drag bit for cutting against the
subterranean formation being
drilled.
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Other modifications and variations of PCD composite materials and compacts
formed therefrom according to the principles of this invention will be
apparent to those skilled in
the art. It is, therefore, to be understood that within the scope of the
appended claims, this
invention may be practiced otherwise than as specifically described.
